Meg Ryan's longer locks

Meg stunned the crowds yesterday when she arrived at the US premier of her new movie, Proof of Life. Her cute, tousled - and much copied - bob had been replaced with what looked like a brand new set of extensions.

Hair extensions have become very popular within the celebrity circuit. Not surprising really - I mean, why wait for your hair to grow when you can pop down to your salon one afternoon and buy yourself a glamorous new mop?

Before you do just that, check out our expert guide to hair extensions, courtesy of Enzo Volpe, Artistic Director at the Michaeljohn salon in London.

How are hair extensions fixed on to the hair?There are two types of extension, Bonded and Woven. The bonded method involves actually glueing the hair in place with a special adhesive while woven extensions are sewn into the real hair with thread. Talk to your stylist beforehand to decide which method is best suited to your particular hair-type.

Does my hair need to be a certain length?

Extensions work on most heads of hair but it's better to have at least 3-4 inches of growth if you want them to look natural.

Both real hair and microfibre extensions come in a wide range of shades that can be matched to your own hair. You can use lighter and darker tones to create different effects or completely change your natural colour.

Can you wash your hair normally?

Synthetic hair is best treated with a gentle fabric conditioner, while real extensions can we washed with your normal shampoo. Both types of extension need to be treated with extra care, to prevent them tearing or working loose.